Electronic component and method for manufacturing the same

ABSTRACT

An electronic component includes a main body composed of an insulator, a coating film covering the main body, a circuit element located inside the main body, and outer electrodes. The insulator contains a metal magnetic powder. The coating film is composed of a resin and a cationic element contained in the insulator.

CROSS REFERENCE TO RELATED APPLICATION

This application claims benefit of priority to Japanese PatentApplication 2014-151348 filed Jul. 25, 2014, and to Japanese PatentApplication 2015-021907 filed Feb. 6, 2015, and to International PatentApplication No. PCT/JP2015/071057 filed Jul. 24, 2015, the entirecontent of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to an electronic component and a methodfor manufacturing the same. In particular, the present disclosurerelates to an electronic component including an insulator containing ametal magnetic powder and a method for manufacturing the same.

BACKGROUND

A coil component described in Japanese Unexamined Patent ApplicationPublication No. 2013-225718 is known as an electronic componentincluding an insulator containing a metal magnetic powder. In this typeof electronic component (hereafter referred to as an electroniccomponent in the related art), an inner circuit element is covered withan insulator containing a metal magnetic powder. In addition, in theelectronic component in the related art, a chemical conversion treatmentwith a phosphate is performed for the purpose of rust prevention and thelike of the metal magnetic powder contained in the insulator. However,in general, coating films formed by employing the chemical conversiontreatment with a phosphate are thin, and the moisture resistance, thechemical resistance, and the like are insufficient for the quality ofthe coating film required for the electronic component.

SUMMARY Technical Problem

It is an object of the present disclosure to provide an electroniccomponent including an insulator containing a metal magnetic powder,where the electronic component has a resin coating film on theinsulator, and a method for manufacturing the same.

Solution to Problem

An electronic component according to the present disclosure includes amain body including an element assembly composed of a metal magneticpowder and an insulating resin and an inner conductor located inside theelement assembly, a coating film covering the main body, and outerelectrodes connected to the inner conductor, wherein the coating filmcontains a cation of an element constituting the metal magnetic powderand a resin.

In the electronic component according to the present disclosure,preferably, the metal magnetic powder is a powder of Fe or an Fe alloy,and the inner conductor is Cu or Ag.

Meanwhile, a method for manufacturing an electronic component, accordingto the present disclosure, includes the steps of preparing a main bodyincluding an element assembly composed of a metal magnetic powder and aninsulating resin and an inner conductor located inside the elementassembly, preparing a resin emulsion containing an etching component forionizing a metal constituting the metal magnetic powder, an anionicsurfactant, and a resin component, coating the main body with the resinemulsion and performing drying, and forming outer electrodes connectedto the inner conductor.

Also, in the method for manufacturing an electronic component accordingto the present disclosure, preferably, the metal magnetic powder is apowder of Fe or an Fe alloy, and the inner conductor is Cu or Ag.

In addition, in the method for manufacturing an electronic componentaccording to the present disclosure, preferably, the etching componentis hydrofluoric acid, sulfuric acid, acetic acid, nitric acid, orhydrochloric acid.

Also, in the method for manufacturing an electronic component accordingto the present disclosure, preferably, the anionic surfactant has asulfonic acid group.

Also, in the method for manufacturing an electronic component accordingto the present disclosure, preferably, the resin emulsion furthercontains an oxidizing agent serving as an etching-facilitationcomponent.

Also, in the method for manufacturing an electronic component accordingto the present disclosure, preferably, the resin emulsion furthercontains iron fluoride serving as an additive.

According to the electronic component of the present disclosure, thecoating film covering the main body is composed of the resin and thecationic element contained in the insulator. The coating film havingsuch a configuration has excellent moisture resistance, chemicalresistance, and the like compared with the coating film formed byemploying a common phosphate chemical conversion treatment.

Also, in the electronic component according to the present disclosure,in the case where the metal magnetic powder is a powder of Fe or an Fealloy and the inner conductor is Cu or Ag, it is possible to make thecoating film easily selectively attach to the metal magnetic powdercontained in the element assembly rather than the inner conductorbecause Fe has an ionization tendency larger than that of Cu or Ag. Onthe other hand, if the coating film is formed on the inner conductor,the continuity between the inner conductor and the outer electrode isdegraded. However, employment of the above-described configuration canavoid degradation of the continuity.

According to the method for manufacturing an electronic component of thepresent disclosure, the steps of preparing a main body including anelement assembly composed of a metal magnetic powder and an insulatingresin and an inner conductor located inside the element assembly,preparing a resin emulsion containing an etching component for ionizinga metal constituting the metal magnetic powder, an anionic surfactant,and a resin component, coating the main body with the resin emulsion andperforming drying, and forming outer electrodes connected to the innerconductor are included and, thereby, an electronic component exhibitingexcellent moisture resistance and chemical resistance can be obtained.

Also, in the method for manufacturing an electronic component accordingto the present disclosure, in the case where the metal magnetic powderis a powder of Fe or an Fe alloy and the inner conductor is Cu or Ag, itis possible to make the coating film easily selectively attach to themetal magnetic powder contained in the element assembly rather than theinner conductor because Fe has an ionization tendency larger than thatof Cu or Ag.

Further, in the method for manufacturing an electronic componentaccording to the present disclosure, in the case where the etchingcomponent is hydrofluoric acid, sulfuric acid, acetic acid, nitric acid,or hydrochloric acid, the film formation property of the coating film isimproved.

Meanwhile, if the surfactant is not easily deactivated, the coating filmis not formed, and if the surfactant is too easily deactivated, theresin emulsion becomes too unstable and is not easily handled. However,in the method for manufacturing an electronic component according to thepresent disclosure, in the case where the anionic surfactant has asulfonic acid group, the degree of deactivation of the surfactant isappropriate.

Further, in the method for manufacturing an electronic componentaccording to the present disclosure, in the case where the resinemulsion further contains an oxidizing agent serving as anetching-facilitation component, ionization of the metal easily proceeds,and formation of the coating film is facilitated.

Also, in the method for manufacturing an electronic component accordingto the present disclosure, in the case where the resin emulsion furthercontains iron fluoride serving as an additive, there is a good balancebetween cations generated by etching with the resin emulsion anddeactivation of the surfactant, and a uniform coating film can beformed.

Advantageous Effects of Disclosure

According to the present disclosure, in an electronic componentincluding an insulator containing a metal magnetic powder, a resincoating film can be obtained on the insulator, and the electroniccomponent exhibiting excellent moisture resistance and chemicalresistance can be obtained.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of an electronic component according to afirst embodiment.

FIG. 2 is an exploded perspective view showing the internal structure ofthe electronic component according to the first embodiment.

FIG. 3 is a sectional view of the electronic component according to thefirst embodiment.

FIG. 4 is a plan view of the electronic component according to the firstembodiment, when viewed from the bottom.

FIG. 5 is a diagram showing a production process of the electroniccomponent according to the first embodiment.

FIG. 6 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 7 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 8 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 9 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 10 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 11 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 12 is a plan view of a columnar electrode at a production stage,when viewed from the bottom.

FIG. 13 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 14 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 15 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 16 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 17 is a diagram showing the production process of the electroniccomponent according to the first embodiment.

FIG. 18 is a diagram showing the manner of a connection reliability test(fixing force test).

FIG. 19 is a perspective view of an electronic component according to asecond embodiment.

FIG. 20 is an exploded perspective view showing the internal structureof the electronic component according to the second embodiment.

FIG. 21 is a sectional view of the electronic component according to thesecond embodiment.

FIG. 22 is a diagram showing a production process of the electroniccomponent according to the second embodiment.

FIG. 23 is a diagram showing the production process of the electroniccomponent according to the second embodiment.

FIG. 24 is a diagram showing the production process of the electroniccomponent according to the second embodiment.

FIG. 25 is a diagram showing the production process of the electroniccomponent according to the second embodiment.

FIG. 26 is a perspective view of an electronic component according to athird embodiment.

FIG. 27 is a sectional view of the electronic component according to thethird embodiment, along a line 27-27 shown in FIG. 26.

DETAILED DESCRIPTION

(First Embodiment)

(Configuration of Electronic Component, Refer to FIG. 1 to FIG. 4)

An electronic component 1 according to a first embodiment will bedescribed with reference to the drawings. Hereafter the directionorthogonal to the bottom surface of the electronic component 1 isdefined as the z-axis direction. Also, in plan view when viewed in thez-axis direction, the direction of the long side of the electroniccomponent 1 is defined as the x-axis direction, and the direction of theshort side of the electronic component 1 is defined as the y-axisdirection. In this regard, the x-axis, the y-axis, and the z-axis areorthogonal to each other.

As shown in FIG. 1, the electronic component 1 includes a main body 10and outer electrodes 20 and 25. In addition, the electronic component 1includes a coating film 9 covering the main body 10 and a circuitelement 30. Also, the electronic component 1 has a substantiallyrectangular parallelepiped shape.

As shown in FIG. 2, the main body 10 includes an element assemblycomposed of insulator layers 11 to 14, an insulator substrate 16, and amagnetic path 18. Also, in the main body 10, the insulator layers 11 and12, the insulator substrate 16, and the insulator layers 13 and 14 arestacked in this order from the positive direction side toward thenegative direction side in the z-axis direction.

The insulator layers 11 and 14 are composed of, for example, an epoxyresin containing a metal magnetic powder. In the present embodiment, inorder to increase the density of the metal magnetic powder in theinsulator layer, the insulator layers 11 and contain two types of metalmagnetic powders having different particle diameters. Specifically, amixed powder of a magnetic powder (maximum particle diameter of 100 μm)composed of an Fe—Si—Cr alloy having an average particle diameter of 80μm and a magnetic powder composed of carbonyl Fe having an averageparticle diameter of 3 μm is employed. In this regard, the metalmagnetic powders may include a powder of Fe or an alloy containing Fe.Examples of the Fe alloys include Fe—Si alloys, Fe—Si—Cr alloys, andFe—Si—Al alloys. Also, an insulating coating serving as an insulatingfilm composed of a metal oxide is applied to these powders in advance byemploying a chemical conversion treatment. The insulating film iscomposed of, for example, a silicon resin, glass, or a metal oxide.Further, in consideration of the L value and direct currentsuperposition characteristics of the electronic component 1, 90 percentby weight or more of metal magnetic powder is contained in the insulatorlayers 11 and 14. In this regard, the resin contained in the insulatorlayers 11 and 14 may be an insulating inorganic material, e.g., a glassceramic, or a polyimide resin. Also, the material for forming theinsulator layers 11 and 14 can be specified to be only the metalmagnetic powder.

Then, the insulator layer 11 is located at the end portion on thepositive direction side in the z-axis direction of the main body 10.Also, the insulator layer 14 is located at the end portion on thenegative direction side in the z-axis direction of the electroniccomponent 1, and a bottom surface S1 that is a surface on the negativedirection side in the z-axis direction of the insulator layer 14 is amounting surface when the electronic component 1 is mounted on a circuitboard. In this regard, the thicknesses of the insulator layers 11 and 14in the present embodiment are about 60 μm and are smaller than themaximum particle diameter of the metal magnetic powder contained in theinsulator layers 11 and 14.

The insulator layers 12 and 13 are composed of an epoxy resin or thelike. Also, the insulator layer 12 is located on the negative directionside in the z-axis direction with respect to the insulator layer 11, andthe insulator layer 13 is located on the positive direction side in thez-axis direction with respect to the insulator layer 14. In this regard,the material for forming the insulator layers 12 and 13 may be aninsulating resin, e.g., benzocyclobutene, or an insulating inorganicmaterial, e.g., a glass ceramic.

The insulator substrate 16 is a printed wiring board, in which a glasscloth is impregnated with an epoxy resin, and is interposed between theinsulator layer 12 and the insulator layer 13 in the z-axis direction.In this regard, the material for forming the insulator substrate 16 maybe an insulating resin, e.g., benzocyclobutene, or an insulatinginorganic material, e.g., a glass ceramic.

The magnetic path 18 is composed of a resin containing a magnetic powderlocated inside the main body 10 almost at the center. Here, in thepresent embodiment, in consideration of the L value and direct currentsuperposition characteristics of the electronic component 1, 90 percentby weight or more of magnetic powder is contained. Further, in order toenhance the filling properties of the magnetic path 18, two types ofmagnetic powders having different particle sizes are mixed as themagnetic powder. Also, the magnetic path 18 penetrates the insulatorlayers 12 and 13 and the insulator substrate 16 in the z-axis direction,and the cross-section has an oval, columnar shape. Further, the magneticpath 18 is disposed so as to be located on inner circumferences of coils32 and 37 described later.

Meanwhile, the surface of the main body 10, that is, the surfaces of theinsulator layers 11 and 14, together with the metal magnetic powderexposed at the surfaces are covered with the coating film 9, as shown inFIG. 3. However, the coating film 9 is not present at the interfacesbetween the insulator layers 11 and 14 and the outer electrodes 20 and25 described later. In addition, the coating film 9 contains Fe, whichis an element constituting the metal magnetic powder contained in anacrylic resin and the insulator layers 11 and 14. Then, the acrylicresin contained in the coating film 9 has a cross-linked structure.Meanwhile, a higher thermal decomposition temperature is preferable inconsideration of the use of solder at the time of mounting theelectronic component 1 onto a circuit board. For example, in the casewhere the thermal decomposition temperature is set to be a temperatureat which about 5% of the mass of the resin constituting the coating film9 decreases, the thermal decomposition temperature is 240° C. or higher.Here, the thermal decomposition temperature can be measured using thefollowing analyzer under the following conditions.

-   -   Analyzer: TG-DTA 2000SA (produced by NETZSCH Japan K.K.)    -   Analysis conditions        -   Temperature profile: RT→300° C. (10° C./min)        -   Measurement atmosphere: reduced pressure (rotary pump is            used: 0.1 Pa)        -   Sample container (cell) material: Al        -   Measurement sample weight: 100 mg

Also, an example of analytical methods for examining ions (cations) ofthe element constituting the metal magnetic powder contained in thecoating film 9 is X-ray photoelectron spectroscopy (XPS). Themeasurement conditions of XPS are as described below.

-   -   Measurement apparatus: PHI 5000 VersaProbe produced by        ULVAC-PHI, Inc.    -   X-ray source: Al—Kα rays    -   Measurement region: 100 μmϕ    -   X-ray acceleration energy: 93.9 eV    -   Time per step of measurement: 100 ms    -   Number of acquisition of Fe2p: 500    -   Energy calibration: C1s=284.6 eV

When the coating film 9 is analyzed by employing XPS, in an Fe2p3spectrum, a peak is recognized at about 710 eV, which indicates thepresence of Fe cations. On the other hand, no peak is recognized atabout 707 eV, which indicates the presence of Fe metal. Consequently,the presence of ions (cations) of an element constituting the metalmagnetic powder contained in the coating film 9 can be verified.

In this regard, the resin components contained in the coating film 9 maybe epoxy resins, polyimide resins, silicone resins, polyamide imideresins, polyether ether ketone resins, fluororesins, acryl siliconeresins, and the like besides the acrylic resins. Examples of resincomponents other than those described above contained in the coatingfilm 9 include acrylic resin emulsions of methyl methacrylate resins,acrylonitrile-styrene-acryl copolymers, and styrene-acryl copolymers.Examples of specific product names include Nipol SX1706A, SX1503A,LX814, and LX855EX by ZEON Corporation and Neocryl A-639, A-655, andA6015 by Kusumoto Chemicals, Ltd.

Meanwhile, there is no particular limitation regarding monomers used forthe resin component contained in the coating film 9, and examplesthereof include (meth)acrylic acid, methyl acrylate, ethyl acrylate,n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate,stearyl acrylate, 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate,diethylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate, methyl methacrylate, propyl methacrylate, n-butylmethacrylate, isobutyl methacrylate, t-butyl methacrylate, n-octylmethacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate, stearylmethacrylate, diethylaminoethyl methacrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, (meth)acrylic acid glycolesters, e.g., ethylene glycol mono(meth)acrylate and polyethylene glycolmono(meth)acrylate, alkyl vinyl ethers, e.g., methyl vinyl ethers andethyl vinyl ethers, vinyl esters, e.g., vinyl acetate,N-alkyl-substituted (meth)acrylamides, e.g., N-methyl acrylamide,N-ethyl acrylamide, N-methyl methacrylamide, and N-ethyl methacrylamide,nitriles, e.g., acrylonitrile and methacrylonitrile, and styrene-basedmonomers, e.g., styrene, ethylene, butadiene, vinyl chloride, vinylidenechloride, vinyl acetate, p-methyl styrene, and α-methyl styrene. Theseother monomers may be used alone, or at least two types may be used incombination. (Meth)acryl refers to acryl or methacryl.

Also, the coating film 9 enters recessed portions C generated by fallingof the metal magnetic powder contained in the insulator layers 11 and 14from the insulator layers 11 and 14, and the recessed portions C arealmost filled therewith. As a result, the thickness d1 of the coatingfilm 9 in the recessed portion C is larger than the thickness d2 of thecoating film 9 in other portions of the surface of the main body 10.

As shown in FIG. 1, the outer electrode 20 is disposed on the bottomsurface S1 and the side surface S2 on the positive direction side in thex-axis direction of the main body 10 when viewed from outside the mainbody 10. Also, the outer electrode 20 is composed of a bottom surfaceelectrode 21 made from a composite material of a metal and a resin and acolumnar electrode 23 made from Cu. In this regard, examples of othermaterials usable for the columnar electrode 23 include Au, Ag, Pd, andNi. Also, the outer electrode 20 produced by an outer electrode formingmethod, e.g., plating or sputtering, in the related art may be used.

The bottom surface electrode 21 is a so-called resin electrode in whicha low-resistance metal powder, that is, a Ag-coated Cu powder having anaverage particle diameter of 100 nm in the present embodiment, isdispersed in a phenol resin. Also, the bottom surface electrode 21 is atabular electrode disposed in a region on the positive direction side inthe x-axis direction of the bottom surface S1 of the insulator layer 14.Further, the bottom surface electrode 21 has a rectangular shape in planview when viewed from the negative direction side in the z-axisdirection.

The columnar electrode 23 is basically disposed in a region on thepositive direction side in the x-axis direction in the main body 10 andis an electrode extending so as to penetrate the insulator layer 14 inthe z-axis direction, as shown in FIG. 2. In this regard, as shown inFIG. 1, the side surface S4 on the positive direction side in the x-axisdirection of the columnar electrode 23 is exposed at the side surface S2of the main body 10. Also, as shown in FIG. 4, the columnar electrode 23has a trapezoidal shape, in which an outer edge L1 exposed at the sidesurface S2 is specified as an upper base and an outer edge L2 located atthe innermost side of the main body 10 is specified as a lower base, inplan view when viewed from the z-axis direction. In this regard, theouter edge L2 is longer than the outer edge L1. Further, in the planview of the columnar electrode 23 when viewed from the z-axis direction,the columnar electrode 23 falls within the bottom surface electrode 21.In addition to this, the area of the side surface S4 of the columnarelectrode 23 is smaller than the area of the bottom surface electrode21. Then, as shown in FIG. 3, the surface on the negative direction sidein the z-axis direction of the columnar electrode 23 (hereafter “surfaceon the negative direction side in the z-axis direction” is referred toas a lower surface) is in contact with the surface on the positivedirection side in the z-axis direction of the bottom surface electrode21 (hereafter “surface on the positive direction side in the z-axisdirection” is referred to as an upper surface).

The outer electrode 25 is an electrode having the same shape as theshape of the outer electrode 20 and is arranged such that the outerelectrode 25 and the outer electrode 20 becomes symmetric with respectto a plane S10 that passes through the central point P1 of the bottomsurface S1 and is parallel to the z-axis and the y-axis. That is, asshown in FIG. 1, the outer electrode 25 is disposed on the bottomsurface S1 and the side surface S3 on the negative direction side in thex-axis direction of the main body 10 when viewed from outside the mainbody 10. Then, the outer electrode 25 is composed of a bottom surfaceelectrode 26 made from the same material for the bottom surface 21electrode and a columnar electrode 28 made from Cu or the like.

The circuit element 30 serving as an inner conductor is located insidethe element assembly in the main body 10 and is composed of anelectrically conductive material, e.g., Au, Ag, Cu, Pd, or Ni. Also, thecircuit element 30 serving as the inner conductor is composed of a coil32, a via conductor 33, a coil 37, and via conductors 38 and 39.

As shown in FIG. 2, the coil 32 is disposed on the upper surface of theinsulator substrate 16 and is a spiral conductor that approaches thecenter while spiraling clockwise in plan view when viewed from thepositive direction side in the z-axis direction. Also, one end on theouter circumference side of the coil 32 extends toward the side surfaceS2 of the main body 10. In this regard, the cross-sectional area of thecross-section orthogonal to the direction of spiraling of the coil 32 issmaller than the cross-sectional area of the cross-section orthogonal tothe z-axis direction, which is the extension direction of the columnarelectrodes 23 and 28.

The via conductor 33 connects one end on the outer circumference side ofthe coil 32 to the columnar electrode 23. Therefore, the via conductor33 penetrates the insulator substrate 16 and the insulator layer 13 inthe z-axis direction.

The coil 37 is disposed on the lower surface of the insulator substrate16, that is, the upper surface of the insulator layer 13, and is aspiral conductor that trends from the center toward the outer sideportion while spiraling clockwise in plan view when viewed from thepositive direction side in the z-axis direction. Also, one end on theouter circumference side of the coil 37 extends toward the side surfaceS3 of the main body 10. Further, the other end on the innercircumference side of the coil 37 is disposed so as to overlap the otherend on the inner circumference side of the coil 32 when viewed from thez-axis direction. In this regard, the cross-sectional area of thecross-section orthogonal to the direction of spiraling of the coil 37 issmaller than the cross-sectional area of the cross-section orthogonal tothe z-axis direction, which is the extension direction of the columnarelectrodes 23 and 28.

The via conductor 38 connects one end on the outer circumference side ofthe coil 37 to the columnar electrode 28. Therefore, the via conductor38 penetrates the insulator layer 13 in the z-axis direction.

The via conductor 39 penetrates the insulator substrate 16 in the z-axisdirection and connects the other end on the inner circumference side ofthe coil 32 to the other end on the inner circumference side of the coil37.

The thus configured electronic component 1 functions as an inductor,where signals input from the outer electrode 20 or the outer electrode25 are output from the outer electrode 20 or the outer electrode 25through the circuit element 30.

(Manufacturing Method, Refer to FIG. 5 to FIG. 17)

A method for manufacturing the electronic component 1 according to thefirst embodiment will be described. The z-axis direction used in theexplanation of the manufacturing method is the direction orthogonal tothe bottom surface of the electronic component 1 produced by themanufacturing method.

Initially, as shown in FIG. 5, a mother insulator substrate 116 servingas the plurality of insulator substrates 16 is prepared. Subsequently,as shown in FIG. 6, a plurality of through holes H1 for disposing viaconductors 39 are formed in the mother insulator substrate 116 by laserbeam machining or the like. In this regard, in order to enhance theacquisition efficiency of the inductance value, the thickness of theinsulator substrate is preferably 60 μm or less.

Then, as shown in FIG. 7, the upper surface and the lower surface of themother insulator substrate 116 provided with the plurality of throughholes are subjected to Cu plating. At this time, the through holes arealso subjected to plating so as to form a plurality of via conductors39. Thereafter, a plurality of conductor patterns 132 and 137corresponding to the coils 32 and 37 are formed on the upper surface andthe lower surface of the mother insulator substrate 116 byphotolithography.

After the plurality of conductor patterns 132 and 137 are formed, Cuplating is further applied so as to obtain a plurality of coils 32 and37 having sufficient diameters, as shown in FIG. 8.

Subsequently, as shown in FIG. 9, the mother insulator substrate 116provided with the plurality of coils 32 and 37 is interposed betweeninsulator sheets 112 and 113 serving as the plurality of insulatorlayers 12 and 13 in the z-axis direction. In this regard, it ispreferable that the step of interposing the coils between the insulatorsheets 112 and 113 be performed in a vacuum for the purpose of makingthe insulator sheets enter very small gaps between the coils. Inaddition to this, in order to suppress generation of stray capacitanceresulting from the coils 32 and 37, the relative dielectric constant ofthe insulator sheets 112 and 113 is preferably 4 or less.

Then, as shown in FIG. 10, a plurality of through holes H2 for disposingvia conductors 33 and 38 are formed in the insulator sheet 113 by laserbeam machining or the like. Further, in order to remove smears generatedby formation of the through holes, desmearing is performed.

After desmearing is performed, first, the insulator sheet 113 issubjected to electroless Cu plating. The electroless plating is for thepurpose of forming a seed layer for electrolytic Cu plating performedthereafter. After the seed layer is formed, the insulator sheet 113 issubjected to electrolytic Cu plating. Consequently, the surface of theinsulator sheet 113 and the through holes are subjected to plating so asto dispose a plurality of via conductors 33 and 38.

Thereafter, as shown in FIG. 11, a plurality of conductor patterns 123having sufficient diameters corresponding to the columnar electrodes 23and 28 are formed on the insulator sheet 113 by photolithography and Cuplating. Here, as shown in FIG. 12, one conductor pattern 123 has ashape, in which upper bases of two trapezoids α and β that are symmetricwith respect to a line are bonded to each other, where the upper basesserve as a symmetry axis γ, when viewed from the z-axis direction.

Subsequently, as shown in FIG. 13, in order to dispose magnetic paths18, a plurality of through holes δ that penetrate the mother insulatorsubstrate 116 and insulator sheets 112 and 113 in the z-axis directionare formed by laser beam machining or the like. In this regard, thelocations of formation of through holes δ are an inner circumferenceside of each of the plurality of coils 32 and 37 disposed on the motherinsulator substrate 116 in the xy plane.

Then, as shown in FIG. 14, a multilayer body, in which the insulatorsheet 112, the mother insulator substrate 116, and the insulator sheet113 are stacked in this order, is interposed between metal magneticpowder-containing resin sheets 111 and 114 corresponding to theinsulator layers 11 and 14 in the z-axis direction and pressure bondingis performed in the same manner as in the case of the insulator sheets112 and 113 shown in FIG. 9. At this time, the metal magneticpowder-containing resin sheet 111 is pressure-bonded from the insulatorsheet 112 side, and the metal magnetic powder-containing resin sheet 114is pressure-bonded from the insulator sheet 113 side. Also, the metalmagnetic powder-containing resin sheets 111 and 114 enter the pluralityof through holes δ by the pressure bonding so as to dispose theplurality of magnetic paths 18. Thereafter, a heat treatment isperformed by using a constant temperature bath, e.g., an oven, so as tocause curing.

Subsequently, the surface of the resin sheet 114 is ground by buffing,lapping, a grinder, and the like. Consequently, as shown in FIG. 15, theconductor patterns 123 are exposed at the surface of the resin sheet114. In this regard, the surface of the resin sheet 111 may be groundfor adjusting the thickness when the resin sheet 114 is ground.

The conductor patterns 123 exposed at the surface of the resin sheet 114are coated with a phenol resin, in which Ag-coated Cu powder having anaverage particle diameter of 100 nm is dispersed, by screen printing,and drying is performed so as to dispose a plurality of resin electrodepatterns 121 corresponding to bottom surface electrodes 21 and 26 on thesurface of the resin sheet 114, as shown in FIG. 16. Consequently, amother substrate 101 that is an aggregate of a plurality of electroniccomponents is completed.

Thereafter, the mother substrate 101 is divided into the plurality ofelectronic components. Specifically, as shown in FIG. 17, the mothersubstrate 101 is divided into the plurality of electronic components bycutting the mother substrate 101 with a dicer or the like such that thesymmetry axis γ, as shown in FIG. 12, located at the center of theconductor pattern 123 agrees with a cut line when viewed from the z-axisdirection. At this time, the conductor pattern 123 is divided into twoparts where the center is the symmetry axis γ, and these serve ascolumnar conductors 23 and 28. In addition, the resin electrode pattern121 is also divided into the bottom surface electrodes 21 and 26.

The plurality of electronic components obtained in the previous step aredipped into a mixed solution (resin emulsion) containing commerciallyavailable latex, in which an etching component and a resin component aredispersed in an aqueous solvent, mixed with an etching-facilitationcomponent and a surfactant. A specific example of composition of themixed solution is shown in Table 1. The surface of each electroniccomponent is etched by the dipping. The etching is caused by actions ofsulfuric acid and hydrogen peroxide contained in the mixed solution. Inthis regard, sulfuric acid is the etching component and hydrogenperoxide is the etching-facilitation component. In the case wherehydrogen peroxide is contained as the etching-facilitation component,ionization of the metal easily proceeds, and formation of the coatingfilm 9 is facilitated. In this regard, no etching-facilitation componentmay be contained in the mixed solution.

TABLE 1 Name of material Amount (ml/l) NipolLATEX SX-1706A 100 ELEMINOLJS-2 35 5% Sulfuric acid 50 30% Aqueous hydrogen peroxide 2 Pure water813

Also, Fe, which is a cationic element serving as a constituent elementof the insulator layers 11 and 14, is ionized by the etching. Further,the ionized cationic element reacts with a resin component contained inan acryl-ester copolymer (NipolLATEX SX-1706A (produced by ZEONCorporation)) in the mixed solution. As a result, the resin component inthe mixed solution is neutralized and deposited on the surface of themain body 10 constituting the electronic component, and the main body 10is covered with the coating film 9. However, the outer electrodes 20 and25 are not covered with the coating film 9. This is because theelectrically conductive material, e.g., Cu, which is the constituentelement of the outer electrodes 20 and 25, is a noble element relativeto Fe and is hardly ionized and, as a result, the electricallyconductive material does not easily react with the resin component.Also, the material for forming the circuit element 30 serving as theinner conductor is an electrically conductive material, e.g., Cu, and,therefore, the circuit element 30 is not covered with the coating film 9as in the cases of the outer electrodes 20 and 25. In this regard,ELEMINOL JS-2 (produced by Sanyo Chemical Industries, Ltd.) contained inthe mixed solution is a surfactant for adjusting the amount of reactionbetween Fe and the resin component.

Thereafter, washing with pure water and draining are performed, and thecoating film 9 is heat-treated. The resin components contained in thecoating film 9 are cross-linked with Fe interposed therebetween or theresin components are cross-linked with each other by the heat treatment.

In this regard, the resin component used for producing the coating film9 may be epoxy resins, polyimide resins, silicone resins, polyamideimide resins, polyether ether ketone resins, fluororesins, acrylsilicone resins, and the like besides the acrylic resin. In addition tothem, examples of resin components contained in the coating film 9include acrylic resin emulsions of methyl methacrylate resins,acrylonitrile-styrene-acryl copolymers, styrene-acryl copolymers, andthe like. Examples of specific product names include Nipol SX1706A,SX1503A, LX814, and LX855EX by ZEON Corporation and Neocryl A-639,A-655, and A6015 by Kusumoto Chemicals, Ltd.

Meanwhile, there is no particular limitation regarding monomers used forthe resin component contained in the coating film 9, and examplesthereof include (meth)acrylic acid, methyl acrylate, ethyl acrylate,n-butyl acrylate, isobutyl acrylate, t-butyl acrylate, dodecyl acrylate,stearyl acrylate, 2-ethylhexyl acrylate, tetrahydrofurfuryl acrylate,diethylaminoethyl acrylate, 2-hydroxyethyl acrylate, 2-hydroxypropylacrylate, methacrylic acid, methyl methacrylate, propyl methacrylate,n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate,n-octyl methacrylate, dodecyl methacrylate, 2-ethylhexyl methacrylate,stearyl methacrylate, diethylaminoethyl methacrylate, 2-hydroxyethylmethacrylate, 2-hydroxypropyl methacrylate, (meth)acrylic acid glycolesters, e.g., ethylene glycol mono(meth)acrylate and polyethylene glycolmono(meth)acrylate, alkyl vinyl ethers, e.g., methyl vinyl ethers andethyl vinyl ethers, vinyl esters, e.g., vinyl acetate,N-alkyl-substituted (meth)acrylamides, e.g., N-methyl acrylamide,N-ethyl acrylamide, N-methyl methacrylamide, and N-ethyl methacrylamide,nitriles, e.g., acrylonitrile and methacrylonitrile, and styrene-basedmonomers, e.g., styrene, ethylene, butadiene, vinyl chloride, vinylidenechloride, vinyl acetate, p-methyl styrene, and α-methyl styrene. Theseother monomers may be used alone, or at least two types may be used incombination. (Meth)acryl refers to acryl or methacryl.

A polymerization initiator used in the step of producing the mixedsolution (resin emulsion) has no influence on the characteristics of thecoating film 9. Also, there is no particular limitation regarding thepolymerization initiator, and any known polymerization initiator can beused. Examples of polymerization initiators include ammonium persulfate,potassium persulfate, t-butylhydroperoxide and, in addition, peroxides,e.g., benzoyl peroxide, lauroyl peroxide,di-t-butylperoxyhexahydroterephthalate, and t-butylperoxyisobutylate,and azo compounds, e.g., azobisisovaleronitrile and2,2-azobis-(2-methylpropionate). Polymerization in the production can beexecuted by performing heating at 40° C. or higher and 90° C. or lowerfor 2 hours or more and 20 hours or less. Examples of polymerizationmethods include emulsion polymerization, soap-free emulsionpolymerization, and suspension polymerization methods.

There is no particular limitation regarding an aqueous solvent. Examplesinclude water and mixed media of water and water-soluble organic media(alcohols, e.g., methanol, ethanol, propanol, butanol, ethylene glycol,glycerin, and 2,2,4-trimethylpentane-1,3-diol monoisobutyrate, glycolethers, e.g., ethylene glycol monoethyl ether and ethylene glycolmonobutyl ether, esters, e.g., 2-ethoxyethyl acetate, and ketones, e.g.,methyl ethyl ketone).

The etching component may be sulfuric acid, hydrofluoric acid, nitricacid, hydrochloric acid, phosphoric acid, and carboxylic acid (forexample, acetic acid). Among them, sulfuric acid, nitric acid,hydrochloric acid, hydrofluoric acid, and acetic acid are particularlypreferably used because the film formation property of the coating film9 is improved. Also, the etching component may be at least two typesselected from hydrofluoric acid, sulfuric acid, acetic acid, nitricacid, and hydrochloric acid.

Also, it is preferable that the etching-facilitation component includean oxidizing agent. Specifically, it is preferable that hydrogenperoxide or a peroxodisulfate be contained as the oxidizing agent. Anexample of the peroxodisulfate is sodium peroxodisulfate.

In this regard, iron fluoride may be mixed as an additive. In the casewhere iron fluoride is contained as an additive, there is a good balancebetween cations generated by etching with the resin emulsion anddeactivation of the surfactant, and a uniform coating film can beformed.

Anionic surfactants and nonionic surfactants are used as the surfactant,and anionic surfactants are particularly preferable. Examples of anionicsurfactants include fatty acid oils, e.g., sodium oleate and castor oilpotassium, alkylsulfuric acid ester salts, e.g., sodium lauryl sulfateand ammonium lauryl sulfate, alkylbenzenesulfonates, e.g., sodiumdodecylbenzenesulfonate, alkylnaphthalenesulfonates, alkanesulfonates,dialkylsulfosuccinates, alkylphosphoric acid ester salts,naphthalenesulfonic acid formalin condensates, polyoxyethylenealkylphenyl ether sulfuric acid ester salts, and polyoxyethylenealkylsulfuric acid ester salts. The above-described surfactants may beused alone or in combination of at least two types. In particular, inthe case where the anionic surfactant has a sulfonic acid group, thedegree of deactivation of the surfactant is appropriate. In this regard,if the surfactant is not easily deactivated, no coating film is formed.If the surfactant is too easily deactivated, the resin emulsion becomesunstable and is not easily handled.

Meanwhile, examples of nonionic surfactants include polyoxyethylenealkyl ethers (alkyl group; octyl, decyl, lauryl, stearyl, oleyl, and thelike), polyoxyethylene alkylphenyl ethers (alkyl group; octyl, nonyl,and the like), and polyoxyethylene⋅polyoxypropylene block copolymers.

Also, water-soluble resins having a sulfonic acid group or a saltthereof, a carboxylic acid or a salt thereof, a phosphoric acid group ora salt thereof, or the like are included.

Further, for the purpose of enhancing the coating film strength and thechemical resistance of the coating film 9, additional treatments may beperformed such that curing agents, for example, amine compounds, e.g.,ethylamine, propylamine, isopropylamine, butylamine, dimethylamine,diethylamine, dipropylamine, dibutylamine, triethylamine,tripropylamine, allylamine, diallylamine, triallylamine,dimethylethanolamine, diethylethanolamine, ethanolamine, diethanolamine,and triethanolamine, amino resins, e.g., melamine resins, guanamineresins, and urea resins, phenol resins, epoxy resins, and isocyanatecompounds are added and a heat treatment is performed.

Finally, in order to improve the wettability of the outer electrodes 20and 25, the surfaces of the outer electrodes 20 and 25 are subjected tonickel plating and tin plating. The electronic component 1 is completedby the above-described steps.

(Advantages)

In the electronic component 1 according to the first embodiment, thecoating film 9 covering the main body 10 is composed of the cationicelement contained in the resin and the insulator layers 11 and 14. Thecoating film 9 having such a configuration is thicker than a coatingfilm formed by employing a phosphate chemical conversion treatment andexhibits excellent abrasion resistance, insulating property, moistureresistance, chemical resistance, and the like. In this regard, thecationic element can be analyzed by using a mapping diagram and an ionstrength profile obtained by time-of-flight secondary ion massspectrometry.

Also, the metal magnetic powder contained in the insulator layers 11 and14 is provided with an insulating coating composed of a metal oxide inadvance by employing a chemical conversion treatment. However, theinsulating coating may peel in a grinding step which is one of theproduction processes of the electronic component 1. Here, in theelectronic component 1, the coating film 9 covering the main body 10 iscomposed of the resin and the cationic element, and the cationic elementis generated from the metal magnetic powder contained in the insulatorlayers 11 and 14 by ionization. Therefore, even in the case where theinsulating coating applied to the metal magnetic powder peels because ofthe grinding step or the like, the cationic element is eluted from themetal magnetic powder during the downstream step so as to form thecoating film 9. As a result, the electronic component 1 exhibits anexcellent insulating property and rust prevention performance.

In addition, even in the case where the insulating coating applied tothe metal magnetic powder peels during the grinding step or the like,the coating film 9 is formed on the metal magnetic powder in thedownstream step, and this contributes to miniaturization and reductionin profile of the electronic component 1. Specifically, in order tominiaturize and reduce the profile of the electronic component 1, it isnecessary to thin the insulator layers 11 and 14 as much as possible.Therefore, the grinding step is an indispensable step in order to thinthe insulator layers 11 and 14. Meanwhile, in the electronic componentin the related art, on the fear that the insulating coating peels offthe metal magnetic powder because of the chemical conversion treatment,the thickness of the insulator layer containing the metal magneticpowder is made larger than the particle diameter of the metal magneticpowder. However, in the electronic component 1, the thicknesses of theinsulator layers 11 and 14 can be made smaller than the particlediameter of the metal magnetic powder because the metal magnetic powderis protected by the coating film 9. As a result, miniaturization andreduction in profile of the electronic component 1 can be realized.

In this regard, in the case where the metal magnetic powder-containingresin is used for the insulator, part of particles of the metal magneticpowder of the machined surface fall by machining, e.g., cutting, andrecessed portions C are generated in the surface of the main body 10,specifically in the surfaces of the insulator layers 11 and 14.Generation of the recessed portions C increases the area that is exposedto the air of the main body 10. As a result, the insulator layers 11 and14 easily absorb moisture in the air. Further, generation of therecessed portions C decreases the distance between the circuit element30 located inside the element assembly in the main body 10 and thesurface of the main body 10. For the above-described reasons, thecircuit element 30 is easily corroded because of generation of therecessed portions C. Here, in the case where a coating film is formed byemploying the phosphate chemical conversion treatment, as in the case ofthe electronic component in the related art, the resulting filmthickness is small and, therefore, it is difficult to fill the recessedportions C. However, in the electronic component 1, the coating film 9composed of the cationic element eluted from the insulator layers 11 and14 and the resin is used rather than the coating film formed byemploying the phosphate chemical conversion treatment. Such a coatingfilm 9 is thicker than the coating film formed by employing thephosphate chemical conversion treatment and, therefore, the recessedportions C generated by falling of particles of the metal magneticpowder can be filled. Consequently, in the electronic component 1,corrosion of the circuit element 30 can be suppressed. That is, theelectronic component 1 exhibits excellent moisture resistance.

Here, the present inventors performed experiments in order to clarifythe effect on the moisture resistance of the electronic component 1. Inthe experiments, 50 first samples corresponding to the electroniccomponent 1 and 50 second samples, in which the coating film 9 in theelectronic component 1 was replaced with the coating film formed byemploying the phosphate chemical conversion treatment, were used and thenormality of the continuity of each sample was examined at a hightemperature and a high humidity. Regarding the specific conditions ofthe experiment, the temperature was 85° C.±2° C. and the humidity was85%±2%, and a current of 6 A was passed continuously. Then, 24 hoursafter start of the experiment, the state of continuity of each samplewas examined. That is, regarding the evaluation criteria, a sample thatexhibited continuity 24 hours after start of the experiment was rated asnon-defective, and a component that exhibited no continuity 24 hoursafter start of the experiment was rated as defective. According to theresults of the experiments, 1 of 50 first samples exhibited nocontinuity and 16 of 50 second samples exhibited no continuity. That is,the defective rate of the first sample was 2%, and the defective rate ofthe second sample was 32%. These results indicate that the moistureresistance of the coating film 9 composed of the cationic element andthe resin is superior to the moisture resistance of the coating filmformed by employing the phosphate chemical conversion treatment.

Meanwhile, the recessed portions C generated by falling of particles ofthe metal magnetic powder are filled with the coating film 9, and thiscontributes to the reliability of connection between the outerelectrodes 20 and 25 of the electronic component 1 and the circuit boardcarrying the electronic component 1. Specifically, in the case whererecessed portions C are present in the surface of the main body 10 nearthe outer electrodes 20 and 25, these recessed portions C cannot befilled with the coating film formed by employing the phosphate chemicalconversion treatment. As a result, when the outer electrodes 20 and 25are subjected to the nickel plating and tin plating, a plating liquidenters the interfaces between the outer electrodes 20 and 25 and themain body 10 from the recessed portions C near the outer electrodes 20and 25, and the outer electrodes 20 and 25 are lifted from the main body10. If the electronic component in this state is soldered to the circuitboard, the fixing force of the electronic component to the circuit boardbecomes insufficient, the reliability of connection between the outerelectrodes 20 and 25 and the circuit board is impaired. On the otherhand, in the electronic component 1 according to the first embodiment,the recessed portions C generated by falling of particles of the metalmagnetic powder are filled with the coating film 9 and, thereby, thereliability of connection between the outer electrodes 20 and 25 and thecircuit board can be maintained.

Here, the present inventors performed experiments in order to examinethe effect on the reliability of connection of the electronic component1. In the experiments, initially, 50 first samples and 50 second sampleswere prepared. Subsequently, each sample was soldered to the circuitboard B1. As shown in FIG. 18, each circuit board B1 was stoodvertically, and a force F was applied to the side surface of each sampledownward in the vertical direction. Then, the force applied to the sidesurface of each sample was measured at the point in time when eachsample came off the circuit board B1.

According to the results of the experiments, the minimum force of thefirst sample was 32 N, and the minimum force of the second sample was 25N. That is, these results indicate that the coating film 9 composed ofthe cationic element and the resin contributes to the reliability ofconnection between the outer electrodes 20 and 25 of the electroniccomponent 1 and the circuit board carrying the electronic component 1.

Meanwhile, in the production steps of the electronic component 1, amixed solution containing commercially available latex, in which anetching component and a resin component are dispersed in an aqueoussolvent, mixed with an etching-facilitation component and a surfactantis used. Consequently, the coating film 9 can be formed at the same timewith etching. Therefore, the production steps of the electroniccomponent 1 are simple compared with the production steps in which asolution of only the etching component and a solution of only the resincomponent are used separately.

Further, in the production steps of the electronic component 1, when thecoating film 9 is formed, Fe contained in the insulator layers 11 and 14is ionized, whereas the electrically conductive material, e.g., Cu,contained in the outer electrodes 20 and 25, the circuit element 30serving as the inner conductor, and the like is hardly ionized. As aresult, the outer electrodes 20 and 25 and the circuit element 30 arenot covered with the coating film 9. That is, in the method formanufacturing the electronic component 1, the coating film 9 can beselectively formed on only a portion in need of coating mainly byutilizing a difference in solubility into the etching component.

(Second Embodiment, Refer to FIG. 19 to FIG. 25)

Different points between an electronic component 1A according to asecond embodiment and the electronic component 1 according to the firstembodiment are the configurations of the outer electrodes 20 and 25, theconfiguration of the circuit element 30, the materials for forming theinsulator layers 12 and 13, the material for forming the insulatorsubstrate 16, and the location at which the coating film 9 is formed.Specific explanations are as described below.

As shown in FIG. 19, in the electronic component 1A, the outer electrode20 is disposed so as to cover the side surface S2 on the positivedirection side in the x-axis direction of the main body 10 and part ofeach of the surfaces surrounding the side surface S2. Also, the outerelectrode 25 is disposed so as to cover the side surface S3 on thenegative direction side in the x-axis direction of the main body 10 andpart of each of the surfaces surrounding the side surface S3.

Further, as shown in FIG. 20, the via conductor 33 is not present in theelectronic component 1A. Instead, as shown in FIG. 21, one end 32 a onthe outer circumference side of the coil 32 serving as the innerconductor is exposed at the side surface S2 of the main body 10.Consequently, the coil 32 is connected to the outer electrode 20. Also,as shown in FIG. 20, the via conductor 38 is not present in theelectronic component 1A. Instead, as shown in FIG. 21, one end 37 a onthe outer circumference side of the coil 37 serving as the innerconductor is exposed at the side surface S3 of the main body 10.Consequently, the coil 37 is connected to the outer electrode 25.

Then, in the electronic component 1A, the material for forming theinsulator layers 12 and 13 and the material for forming the insulatorlayer 16 are composed of the same metal magnetic powder-containing resinas the material for forming the insulator layers 11 and 14.

Meanwhile, in the electronic component 1A, the configurations of theouter electrodes 20 and 25 and the like are different from those in theelectronic component 1 and, therefore, the manufacturing method ispartly different. In production of the electronic component 1A, a motherinsulator substrate 116 provided with a plurality of coils 32 and 37 isinterposed between two insulator sheets 112 and 113 as in the case shownin FIG. 9. Thereafter, the through holes δ for forming the magneticpaths 18 are formed, as shown in FIG. 22. In this regard, the materialfor constituting the mother insulator substrate 116 and the insulatorsheets 112 and 113 is the metal magnetic powder-containing resin.

Subsequently, as shown in FIG. 23, the multilayer body, in which theinsulator sheet 112, the mother insulator substrate 116, and theinsulator sheet 113 are stacked in this order, is interposed between theinsulator sheets 111 and 114 in the z-axis direction and pressurebonding is performed, as in the case of the insulator sheets 112 and 113shown in FIG. 9. The metal magnetic powder-containing resin sheets 111and 114 enter the plurality of through holes δ by this pressure bondingso as to dispose the plurality of magnetic paths 18. Thereafter, a heattreatment is performed by using a constant temperature bath, e.g., anoven, so as to cause curing.

After the curing, in order to adjust the thicknesses, the surfaces ofthe resin sheets 111 and 114 are ground by buffing, lapping, a grinder,or the like. Consequently, a mother substrate that is an aggregate of aplurality of electronic components is completed.

Then, as shown in FIG. 24, the mother substrate is divided into theplurality of electronic components by being cut with a dicer or thelike. One end 32 a on the outer circumference side of the coil 32 andone end 37 a on the outer circumference side of the coil 37 are exposedat the cut surfaces by this division.

The plurality of electronic components obtained in the previous step aredipped into a mixed solution (resin emulsion) containing commerciallyavailable latex, in which an etching component and a resin component aredispersed in an aqueous solvent, mixed with an etching-facilitationcomponent and a surfactant. In this regard, no etching-facilitationcomponent may be contained in the mixed solution. Consequently, thesurface of the main body 10 constituting the electronic component iscovered with the coating film 9. However, the one end 32 a on the outercircumference side of the coil 32 and one end 37 a on the outercircumference side of the coil 37 are not covered with the coating film9. This is because the electrically conductive material, e.g., Cu, whichis the constituent element of the coils 32 and 37 serving as the innerconductors, is a noble element relative to Fe and is hardly ionized and,as a result, the electrically conductive material does not easily reactwith the resin component.

Thereafter, washing with pure water and draining are performed, and thecoating film 9 is heat-treated. The resin components contained in thecoating film 9 are cross-linked with Fe interposed therebetween or theresin components are cross-linked with each other by the heat treatment.

Finally, the outer electrodes 20 and 25 are formed. First, the main body10 covered with the coating film 9 is coated with an electrode pastecomposed of an electrically conductive material containing Ag as aprimary component. Subsequently, the resulting electrode paste isheat-treated at a temperature of 80° C. to 200° C. for 5 to 12 minutes,for example. The surfaces of the thus formed underlying electrodes ofthe outer electrodes 20 and 25 are subjected to copper plating, nickelplating, and tin plating so as to form the outer electrodes 20 and 25.The electronic component 1A is completed by the above-described steps.

(Advantages)

In the electronic component 1A having the above-described configuration,the outer electrodes 20 and 25 are disposed after the coating film 9 isformed. Therefore, as shown in FIG. 21, the coating film 9 is present atthe interfaces between the main body 10 and the outer electrodes 20 and25. Here, the reliability of connection between the outer electrodes 20and 25 of the electronic component 1A and the circuit board carrying theelectronic component 1A is improved because the coating film 9 ispresent at the interfaces between the main body 10 and the outerelectrodes 20 and 25. Specific explanations are as described below.

In the case where the metal magnetic powder-containing resin is used forthe insulator, part of particles of the metal magnetic powder of themachined surface fall by machining, e.g., cutting, and recessed portionsC are generated in the surface of the main body 10. For example, in thesecond embodiment, recessed portions C are generated in the sidesurfaces S2 and S3. If the outer electrodes 20 and 25 are formeddirectly on the recessed portions C, covering of the Ag underlyingelectrode with the copper plating, nickel plating, and tin platingbecomes insufficient. As a result, so-called solder leaching occurs,where almost all copper plating, nickel plating, and tin plating on therecessed portions C are eluted into solder. If solder leaching occurs,the Ag underlying electrode is exposed, connection with solder becomesimpossible or insufficient, and the reliability of connection betweenthe outer electrodes 20 and 25 and the circuit board carrying theelectronic component 1A is impaired. However, in the electroniccomponent 1A, the recessed portions C are filled with the coating film 9and, thereby, the Ag underlying electrode is sufficiently covered withthe copper plating, nickel plating, and tin plating. Therefore,regarding the electronic component 1A, the reliability of connectionbetween the outer electrodes 20 and 25 of the electronic component 1Aand the circuit board carrying the electronic component 1A can beimproved because the coating film 9 is present at the interfaces betweenthe main body 10 and the outer electrodes 20 and 25.

Here, the present inventors examined the effect on the reliability ofconnection of the electronic component 1A by using 50 third samplescorresponding to the electronic component 1A. The experiment forexamining the reliability of connection was the same as the experimentsperformed with respect to the first sample and the second sample.According to the results of the experiment, the minimum force of thethird sample was 35 N. That is, the result indicates that the coatingfilm 9 composed of the cationic element and the resin improves thereliability of connection between the outer electrodes 20 and 25 of theelectronic component 1A and the circuit board carrying the electroniccomponent 1A.

In addition, the present inventors examined the effect on the moistureresistance by using 50 third samples. The experiment for examining themoisture resistance was the same as the experiments performed withrespect to the first sample and the second sample. According to theresults of the experiment, the defective rate of the third sample was4%. The result indicates that in the electronic component 1A as well,the moisture resistance of the coating film 9 composed of the cationicelement and the resin is superior to the moisture resistance of thecoating film formed by employing the phosphate chemical conversiontreatment.

(Third Embodiment, Refer to FIG. 26 and FIG. 27)

The present disclosure can further be applied to an electronic componentaccording to a third embodiment, as shown in FIG. 26. FIG. 26 is aperspective view of an electronic component according to the thirdembodiment. FIG. 27 is a sectional view of the electronic componentaccording to the third embodiment, along a line 27-27 shown in FIG. 26.

As shown in FIG. 26, the electronic component 1B includes a main body 10and outer electrodes 20 and 25. The main body 10 is formed so as to havea substantially rectangular parallelepiped shape and include an elementassembly 10 a formed from the same metal magnetic powder-containingresin as in the case of the insulator layers 11 and 14. A coil 35serving as an inner conductor is included inside the element assembly 10a. The coil 35 is formed by using a conductor wire and is formed byspirally outwardly winding the conductor wire in two stages such thatthe end portions 35 a and 35 b of the conductor wire are located atoutermost turns. The end portions 35 a and 35 b of the coil 35 areexposed at the surface (side surface on the positive direction side inthe y-axis direction) of the main body 10.

Meanwhile, in the electronic component 1B, as shown in FIG. 26, theouter electrode 20 is disposed so as to cover the side surface S2 on thepositive direction side in the x-axis direction of the main body 10 andpart of each of the surfaces surrounding the side surface S2. Also, theouter electrode 25 is disposed so as to cover the side surface S3 on thenegative direction side in the x-axis direction of the main body 10 andpart of each of the surfaces surrounding the side surface S3.Consequently, the outer electrode 20 is connected to the end portion 35a, and the outer electrode 25 is connected to the end portion 35 b.Then, as shown in FIG. 27, the electronic component 1B is configuredsuch that the coating film 9 is present at the interfaces between themain body 10 and the outer electrodes 20 and 25.

Next, a method for manufacturing the electronic component 1B accordingto the third embodiment will be described.

Initially, the coil 35 serving as an inner conductor is formed andprepared by using a conductor wire.

Thereafter, the coil 35 is interposed between insulator sheets servingas the element assembly 10 a and containing the same metal magneticpowder as that in the case of the insulator layers 11 and 14 in thevertical direction by employing a compression molding method so as toform the main body 10. At this time, forming is performed such that theend portions 35 a and 35 b of the coil 35 are exposed at the surface(side surface on the positive direction side in the y-axis direction) ofthe main body 10.

Subsequently, a mixed solution (resin emulsion) containing commerciallyavailable latex, in which an etching component for ionizing the metalconstituting the metal magnetic powder contained in the element assembly10 a and a resin component are dispersed in an aqueous solvent, mixedwith an etching-facilitation component and a surfactant is prepared. Inthis regard, no etching-facilitation component may be contained in themixed solution. Then, the resulting main body 10 is dipped into theprepared mixed solution. Consequently, the surface of the main body 10constituting the electronic component is covered with the mixedsolution, and the surface of the main body 10 is etched. However, theend portion 35 a (35 b) of the coil 35 is not etched and, therefore, thecoating film 9 is not formed on the surface of the end portion 35 a (35b) of the coil 35 (refer to FIG. 27). This is because the electricallyconductive material, e.g., Cu, which is the constituent element of thecoil 35 serving as the inner conductor, is a noble element relative toFe and is hardly ionized and, as a result, the electrically conductivematerial does not easily react with the resin component.

In this regard, as a matter of course, the same material as the materialused in the method for manufacturing the electronic component 1according to the first embodiment can be used for each of the resincomponent, the aqueous solvent, the etching component, and thesurfactant contained in the mixed solution.

Thereafter, washing with pure water and draining are performed, and themain body 10, the surface of which has been etched by being covered withthe mixed solution, is subjected to a heat (drying) treatment. The resincomponents contained in the mixed solution are cross-linked with Fe,which is the metal magnetic powder, interposed therebetween or the resincomponents are cross-linked with each other by employing the heattreatment and, thereby, the coating film 9 is formed on the surface ofthe main body 10, as shown in FIG. 27.

Finally, the outer electrodes 20 and 25 are formed on the main body 10provided with the coating film. First, the main body 10 covered with thecoating film 9 is coated with an electrode paste composed of anelectrically conductive material containing Ag as a primary component.Subsequently, the resulting electrode paste is heat-treated at atemperature of 80° C. to 200° C. for 5 to 12 minutes, for example.Consequently, the surfaces of the thus formed underlying electrodes ofthe outer electrodes 20 and 25 are subjected to copper plating, nickelplating, and tin plating so as to form the outer electrodes 20 and 25.The electronic component 1B is completed through the above-describedsteps.

The electronic component 1B having the above-described configurationexerts the same effects as in the cases of the electronic component 1 orthe electronic component 1A. That is, the electronic component 1Baccording to the third embodiment exhibits excellent reliability ofconnection and moisture resistance.

Here, the present inventors produced a sample of each of the examplescorresponding to the electronic component 1B and the comparativeexamples. In the sample of each of the examples and the comparativeexamples, the material and the content of the resin component, theetching component, the surfactant, and the etching-facilitationcomponent contained in the mixed solution (resin emulsion) for formingthe coating film 9 were changed variously. In the experimental examples,experiments for examining the reliability of connection and the moistureresistance of the sample of each of the examples and the comparativeexamples were performed.

EXAMPLES

To begin with, the sample of each of Example 1 to Example 29 shown inTable 2 was produced following the above-described method formanufacturing the electronic component. Here, the coating film 9 wasformed by performing dipping into the mixed solution for 5 minutes,performing washing with pure water, and thereafter, performing heatingin an oven at 180° C. for 10 minutes so as to cause curing. In eachexperiment, 100 samples corresponding to the electronic component 1B ofeach of Example 1 to Example 29 were prepared.

In Example 1, the resin component contained in the mixed solution forforming the coating film 9 was set to be an acryl-ester copolymer (tradename: Nipol SX1706A (produced by ZEON Corporation)), the etchingcomponent was set to be sulfuric acid, the surfactant was set to besodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2 (produced bySanyo Chemical Industries, Ltd.)), and the etching-facilitationcomponent and the additive were not contained.

In Example 2, the resin component contained in the mixed solution forforming the coating film 9 was set to be an acryl-ester copolymer (tradename: Nipol SX1706A (produced by ZEON Corporation)), the etchingcomponent was set to be sulfuric acid, the surfactant was set to besodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2 (produced bySanyo Chemical Industries, Ltd.)), the additive was set to be iron(III)fluoride, and the etching-facilitation component was not contained.

In Example 3 to Example 5, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the etching component was set to be sulfuric acid, the surfactant wasset to be sodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2(produced by Sanyo Chemical Industries, Ltd.)), the etching-facilitationcomponent was set to be hydrogen peroxide and, in addition, the contentof the resin component relative to the mixed solution was changed in therange of 0.5 g to 1.5 g.

In Example 6 to Example 8, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the etching component was set to be sulfuric acid, the surfactant wasset to be sodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2(produced by Sanyo Chemical Industries, Ltd.)), the etching-facilitationcomponent was set to be hydrogen peroxide, the additive was set to beiron(III) fluoride and, in addition, the content of the sulfuric acidserving as the etching component relative to the mixed solution waschanged in the range of 0.02 g to 0.1 g. In this regard, the content ofthe surfactant was set to be 0.2 g in Example 6 and Example 7 and wasset to be 0.1 g in Example 8.

In Example 9 to Example 11, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the etching component was set to be sulfuric acid, the surfactant wasset to be sodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2(produced by Sanyo Chemical Industries, Ltd.)), the etching-facilitationcomponent was set to be hydrogen peroxide, the additive was set to beiron(III) fluoride and, in addition, the content of theetching-facilitation component relative to the mixed solution waschanged in the range of 0.01 g to 0.3 g. In this regard, the content ofthe surfactant was set to be 0.5 g in Example 9 and was set to be 0.2 gin Example 10 and Example 11.

In Example 12 to Example 14, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the etching component was set to be sulfuric acid, the surfactant wasset to be sodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2(produced by Sanyo Chemical Industries, Ltd.)), the etching-facilitationcomponent was set to be hydrogen peroxide, the additive was set to beiron(III) fluoride and, in addition, the content of sulfuric acidserving as the etching component relative to the mixed solution waschanged in the range of 0 g (not contained) to 0.005 g.

In Example 15, the resin component contained in the mixed solution forforming the coating film 9 was set to be an acryl-ester copolymer (tradename: Nipol SX1706A (produced by ZEON Corporation)), the etchingcomponent was set to be sulfuric acid, the surfactant was set to besodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2 (produced bySanyo Chemical Industries, Ltd.)), the etching-facilitation componentwas set to be sodium peroxodisulfate, and the additive was set to beiron(III) fluoride.

In Example 16 to Example 18, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the etching component was set to be sulfuric acid, theetching-facilitation component was set to be hydrogen peroxide, and theadditive was set to be iron(III) fluoride. Then, the surfactantcontained in the mixed solution for forming the coating film 9 was setto be β-naphthalenesulfonic acid formalin condensate sodium salt (tradename: DEMOL N (produced by Kao Corporation)) in Example 16, was set tobe sodium dioctylsulfosuccinate (trade name: RAPISOL A-80 (produced byNOF CORPORATION)) in Example 17, and was set to be straight-chain sodiumalkylbenzenesulfonate (NEWREX R (produced by NOF CORPORATION)) inExample 18.

The resin component contained in the mixed solution for forming thecoating film 9 was set to be a styrene-acryl copolymer (trade name:Neocryl A-655 (produced by Kusumoto Chemicals, Ltd.)) in Example 19 andwas set to be an acryl-ester copolymer (trade name: Nipol LX814(produced by ZEON Corporation)) in Example 20. Also, in Example 19 andExample 20, the etching component contained in the mixed solution forforming the coating film 9 was set to be sulfuric acid, the surfactantwas set to be sodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2(produced by Sanyo Chemical Industries, Ltd.)), the etching-facilitationcomponent was set to be hydrogen peroxide, and the additive was set tobe iron(III) fluoride.

In Example 21 to Example 23, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the surfactant was set to be sodium alkylallylsulfosuccinate (tradename: ELEMINOL JS-2 (produced by Sanyo Chemical Industries, Ltd.)), theetching-facilitation component was set to be hydrogen peroxide, and theadditive was set to be iron(III) fluoride. Then, the etching componentcontained in the mixed solution for forming the coating film 9 was setto be nitric acid in Example 21, was set to be hydrochloric acid inExample 22, and was set to be acetic acid in Example 23.

In Example 24 to Example 26, the resin component contained in the mixedsolution for forming the coating film 9 was set to be an acryl-estercopolymer (trade name: Nipol SX1706A (produced by ZEON Corporation)),the etching component was set to be hydrofluoric acid, the surfactantwas set to be sodium alkylallylsulfosuccinate (trade name: ELEMINOL JS-2(produced by Sanyo Chemical Industries, Ltd.)), the etching-facilitationcomponent was set to be hydrogen peroxide, the additive was set to beiron(III) fluoride and, in addition, the content of hydrofluoric acidserving as the etching component relative to the mixed solution waschanged in the range of 0.02 g to 0.1 g.

The resin component contained in the mixed solution for forming thecoating film 9 was set to be a silicone resin (trade name: POLON-MF-56(produced by Shin-Etsu Silicone)) in Example 27, was set to be asilicone resin (trade name: X-51-1318 (produced by Shin-Etsu Silicone))in Example 28, and was set to be an epoxy-acryl resin (trade name:MODEPICS-302 (produced by ARAKAWA CHEMICAL INDUSTRIES LTD.)) in Example29. Also, in Example 27 to Example 29, the etching component containedin the mixed solution for forming the coating film 9 was set to behydrofluoric acid, the surfactant was set to be sodiumalkylallylsulfosuccinate (trade name: ELEMINOL JS-2 (produced by SanyoChemical Industries, Ltd.)), the etching-facilitation component was setto be hydrogen peroxide, and the additive was set to be iron(III)fluoride.

Next, the sample of each of Comparative example 1 and Comparativeexample 2 shown in Table 3 was produced. In each experiment, 100 samplesof each of Comparative example 1 and Comparative example 2 wereprepared.

(Comparative Examples)

In Comparative example 1, the coating film 9 of the electronic component1B was formed by employing the phosphate chemical conversion treatment.

Meanwhile, in Comparative example 2, the resin component contained inthe mixed solution for forming the coating film 9 was set to be anacryl-ester copolymer (trade name: Nipol SX1706A (produced by ZEONCorporation)), the surfactant was set to be sodiumalkylallylsulfosuccinate (trade name: ELEMINOL JS-2 (produced by SanyoChemical Industries, Ltd.)), the additive was set to be iron(III)fluoride, and the etching component and the etching-facilitationcomponent were not contained.

(Evaluation Method)

The experiment for evaluating the reliability of connection of theelectronic component 1B was performed. The experiment for examining thereliability of connection (fixing force test) was the same as theexperiments performed with respect to the electronic component 1according to the first embodiment and the electronic component 1Aaccording to the second embodiment. That is, as shown in FIG. 18, eachsample was soldered to the circuit board B1, the circuit board B1 wasstood vertically, and a force F was applied to the side surface of eachsample downward in the vertical direction. Then, the force applied tothe side surface of each sample was measured at the point in time wheneach sample came off the circuit board B1.

In addition, the experiment for evaluating the moisture resistance ofthe electronic component 1B was performed. The experiment for examiningthe moisture resistance (moisture resistance test) was the same as theexperiments performed with respect to the electronic component 1according to the first embodiment and the electronic component 1Aaccording to the second embodiment. That is, the normality of thecontinuity of each sample was examined at a high temperature and a highhumidity. Regarding the specific conditions of the experiment, thetemperature was 85° C.±2° C. and the humidity was 85%±2%, and a currentof 6 A was passed continuously. Then, 24 hours after start of theexperiment, the state of continuity of the evaluation sample wasexamined. That is, regarding the evaluation criteria, a sample thatexhibited continuity 24 hours after start of the experiment was rated asnon-defective, and a component that exhibited no continuity 24 hoursafter start of the experiment was rated as defective. Then, regardingthe samples, the case where the probability of non-defective samplesbeing included (non-defective rate) was 70% or more was rated asnon-defective.

Table 2 shows the evaluation results of Example 1 to Example 29.

In addition, Table 3 shows the evaluation results of Comparative example1 and Comparative example 2.

TABLE 2 Surfactant Resin component component Amount Type OxidizingNumber Type (solid Etching component (trade agent No. (trade name)content) Type Amount name) Amount Type Amount Example 1 Nipol 1 gsulfuric acid 0.05 g ELEMINOL 0.2 g — — SX1706A JS-2 2 Nipol 1 gsulfuric acid 0.05 g ELEMINOL 0.2 g — — SX1706A JS-2 3 Nipol 0.5 g  sulfuric acid 0.05 g ELEMINOL 0.2 g hydrogen 0.06 g SX1706A JS-2peroxide 4 Nipol 1 g sulfuric acid 0.05 g ELEMINOL 0.2 g hydrogen 0.06 gSX1706A JS-2 peroxide 5 Nipol 1.5 g   sulfuric acid 0.05 g ELEMINOL 0.2g hydrogen 0.06 g SX1706A JS-2 peroxide 6 Nipol 1 g sulfuric acid 0.02 gELEMINOL 0.2 g hydrogen 0.06 g SX1706A JS-2 peroxide 7 Nipol 1 gsulfuric acid 0.10 g ELEMINOL 0.2 g hydrogen 0.06 g SX1706A JS-2peroxide 8 Nipol 1 g sulfuric acid 0.05 g ELEMINOL 0.1 g hydrogen 0.06 gSX1706A JS-2 peroxide 9 Nipol 1 g sulfuric acid 0.05 g ELEMINOL 0.5 ghydrogen 0.06 g SX1706A JS-2 peroxide 10 Nipol 1 g sulfuric acid 0.05 gELEMINOL 0.2 g hydrogen 0.01 g SX1706A JS-2 peroxide 11 Nipol 1 gsulfuric acid 0.05 g ELEMINOL 0.2 g hydrogen 0.30 g SX1706A JS-2peroxide 12 Nipol 1 g sulfuric acid 0.05 g ELEMINOL 0.2 g hydrogen 0.06g SX1706A JS-2 peroxide 13 Nipol 1 g sulfuric acid 0.05 g ELEMINOL 0.2 ghydrogen 0.06 g SX1706A JS-2 peroxide 14 Nipol 1 g sulfuric acid 0.05 gELEMINOL 0.2 g hydrogen 0.06 g SX1706A JS-2 peroxide 15 Nipol 1 gsulfuric acid 0.05 g ELEMINOL 0.2 g sodium 0.06 g SX1706A JS-2peroxodisulfate 16 Nipol 1 g sulfuric acid 0.05 g DEMOL N 0.2 g hydrogen0.06 g SX1706A peroxide 17 Nipol 1 g sulfuric acid 0.05 g RAPISOL A- 0.2g hydrogen 0.06 g SX1706A 80 peroxide 18 Nipol 1 g sulfuric acid 0.05 gNEWREX R 0.2 g hydrogen 0.06 g SX1706A peroxide 19 Neocryl A- 1 gsulfuric acid 0.05 g ELEMINOL 0.2 g hydrogen 0.06 g 655 JS-2 peroxide 20Nipol LX814A 1 g sulfuric acid 0.05 g ELEMINOL 0.2 g hydrogen 0.06 gJS-2 peroxide 21 Nipol 1 g nitric acid 0.05 g ELEMINOL 0.2 g hydrogen0.06 g SX1706A JS-2 peroxide 22 Nipol 1 g hydrochloric 0.05 g ELEMINOL0.2 g hydrogen 0.06 g SX1706A acid JS-2 peroxide 23 Nipol 1 g aceticacid 0.05 g ELEMINOL 0.2 g hydrogen 0.06 g SX1706A JS-2 peroxide 24Nipol 1 g hydrofluoric 0.02 g ELEMINOL 0.2 g hydrogen 0.06 g SX1706Aacid JS-2 peroxide 25 Nipol 1 g hydrofluoric 0.05 g ELEMINOL 0.2 ghydrogen 0.06 g SX1706A acid JS-2 peroxide 26 Nipol 1 g hydrofluoric0.10 g ELEMINOL 0.2 g hydrogen 0.06 g SX1706A acid JS-2 peroxide 27POLON-MF- 1 g hydrofluoric 0.05 g ELEMINOL 0.2 g hydrogen 0.06 g 56 acidJS-2 peroxide 28 X-51-1318 1 g hydrofluoric 0.05 g ELEMINOL 0.2 ghydrogen 0.06 g acid JS-2 peroxide 29 MODEPICS- 1 g hydrofluoric 0.05 gELEMINOL 0.2 g hydrogen 0.06 g 302 acid JS-2 peroxide Moisture Fixingresistance force test test Minimum Average Non- Number Additive Solventvalue value defective rate No. Type Amount Type Amount [N] [N] [%]Example 1 — — pure 15.7 g 23 24 70 water 2 iron(III) 0.002 g pure 15.7 g25 26 70 fluoride water 3 iron(III) 0.002 g pure 15.7 g 32 33 92fluoride water 4 iron(III) 0.002 g pure 15.7 g 32 34 95 fluoride water 5iron(III) 0.002 g pure 15.7 g 29 30 95 fluoride water 6 iron(III) 0.002g pure 15.7 g 32 34 91 fluoride water 7 iron(III) 0.002 g pure 15.7 g 3234 95 fluoride water 8 iron(III) 0.002 g pure 15.7 g 30 33 94 fluoridewater 9 iron(III) 0.002 g pure 15.7 g 30 32 92 fluoride water 10iron(III) 0.002 g pure 15.7 g 31 32 91 fluoride water 11 iron(III) 0.002g pure 15.7 g 31 34 93 fluoride water 12 iron(III) 0.0005 g  pure 15.7 g32 34 90 fluoride water 13 iron(III) 0.005 g pure 15.7 g 32 33 94fluoride water 14 — — pure 15.7 g 31 31 84 fluoride water 15 iron(III)0.002 g pure 15.7 g 32 33 94 fluoride water 16 iron(III) 0.002 g pure15.7 g 29 30 81 fluoride water 17 iron(III) 0.002 g pure 15.7 g 31 32 91fluoride water 18 iron(III) 0.002 g pure 15.7 g 30 32 90 fluoride water19 iron(III) 0.002 g pure 15.7 g 30 30 85 fluoride water 20 iron(III)0.002 g pure 15.7 g 30 33 90 fluoride water 21 iron(III) 0.002 g pure15.7 g 32 33 87 fluoride water 22 iron(III) 0.002 g pure 15.7 g 30 31 92fluoride water 23 iron(III) 0.002 g pure 15.7 g 30 30 86 fluoride water24 iron(III) 0.002 g pure 15.7 g 31 34 94 fluoride water 25 iron(III)0.002 g pure 15.7 g 34 37 99 fluoride water 26 iron(III) 0.002 g pure15.7 g 32 34 95 fluoride water 27 iron(III) 0.002 g pure 15.7 g 28 29 98fluoride water 28 iron(III) 0.002 g pure 15.7 g 27 29 99 fluoride water29 iron(III) 0.002 g pure 15.7 g 30 32 94 fluoride water

TABLE 3 Surfactant Resin component component Amount Etching TypeOxidizing Number Type (solid component (trade agent No. (trade name)content) Type Amount name) Amount Type Amount Comparative 1 phosphate —— — — — — — example chemical conversion treatment 2 Nipol — — — ELEMINOL— — — SX1706A JS-2 Moisture resistance Fixing force test test NumberAdditive Solvent Minimum Average Non-defective No. Type Amount TypeAmount value [N] value [N] rate [%] Comparative 1 — — — — 25 26 67example 2 iron(III) 0.002 g pure — — — — fluoride water

As shown in Table 2, in the case of Example 1 to Example 29, the coatingfilm 9 is formed by using the mixed solution (resin emulsion) containingthe etching component for ionizing the metal constituting the metalmagnetic powder, the anionic surfactant, and the resin component and,thereby, the minimum force of the force F applied to the side surface ofeach sample was 23 N in the fixing force test, and all non-defectiverates were 70% or more in the moisture resistance test. Therefore, goodresults were obtained in all Examples.

On the other hand, as shown in Table 3, in the case of Comparativeexample 1, the coating film was formed by employing the phosphatechemical conversion treatment and, thereby, the minimum force of theforce F applied to the side surface of the sample was 25 N, whereas thenon-defective rate was 67% in the moisture resistance test. Therefore,the sample was rated as defective. Also, in the case of Comparativeexample 2, the coating film was not formed because the etching componentwas not contained in the mixed solution (resin emulsion) for forming thecoating film. Therefore, the fixing force test and the moistureresistance test were not able to be performed.

In this regard, in the case where the coating film 9 is formed on themain body 10, the film formation property of the coating film 9 isimportant. The film formation property is evaluated on the basis of theclose contact of the coating film 9 with the main body 10, theuniformity of the coating film 9, and the deposition property, whichindicates that a neutralization reaction is not excessively slow and theresin component constituting the coating film 9 deposits on the mainbody 10 in a shorter time. Among them, the deposition property isparticularly important from the viewpoint of production efficiency.

According to the results of the present experiments, when attention isgiven to the resin component, all resin components in the examplesexhibited good film formation property. In particular, the filmformation property (deposition property) was good in the order of theacryl-ester copolymer (trade name: Nipol SX1706A (produced by ZEONCorporation)), the acryl-ester copolymer (trade name: Nipol LX814(produced by ZEON Corporation)), and the styrene-acryl copolymer (tradename: Neocryl A-655 (produced by Kusumoto Chemicals, Ltd.)).

Also, when attention is given to the etching component, all etchingcomponents in the examples exhibited good film formation property. Inparticular, the film formation property (deposition property) was goodin the order of hydrofluoric acid, sulfuric acid, acetic acid, nitricacid, and hydrochloric acid.

Also, when attention is given to the surfactant, all surfactants in theexamples exhibited good film formation property. In particular, the filmformation property (deposition property) was good in the order of sodiumalkylallylsulfosuccinate (trade name: ELEMINOL JS-2 (produced by SanyoChemical Industries, Ltd.)), straight-chain sodium alkylbenzenesulfonate(NEWREX R (produced by NOF CORPORATION)), sodium dioctylsulfosuccinate(trade name: RAPISOL A-80 (produced by NOF CORPORATION)), andβ-naphthalenesulfonic acid formalin condensate sodium salt (trade name:DEMOL N (produced by Kao Corporation)).

Further, when Example 1 and other Examples are compared, the result ofthe fixing force test of the electronic component 1B, in which iron(III)fluoride was contained in the mixed solution, was better than the resultof the fixing force test of the electronic component 1B, in whichiron(III) fluoride was not contained.

In this regard, the electronic component and the method formanufacturing the same according to the present disclosure are notlimited to the above-described embodiments and can be variously modifiedwithin the scope of the gist thereof.

Regarding the mixed solution for forming the coating film 9, tannin forimproving the corrosion resistance, plasticizers, e.g.,dibutylphthalate, for imparting the flexibility to the coating film 9,metal ions, e.g., silver fluoride, for improving the film formationproperty of the coating film 9, and lubricants, e.g., fluororesinlubricants, polyolefin wax, melamine cyanurate, and molybdenumdisulfide, for preventing scratching of the surface and improving thewater resistance of the coating film 9 may be added to the mixedsolution.

Further, for the purpose of improving the corrosion resistance of thecoating film 9 and coloring the electronic component, pigments, e.g.,carbon black and phthalocyanine blue, may be added to the mixed solutionfor forming the coating film 9.

In addition, the corrosion resistance and the chemical resistance can beimproved by adding a high-molecular-weight polymer having an acid groupcontaining phosphorus, for example, an organic high-molecular-weightcompound having a phosphoric acid group, a phosphorous acid group, aphosphonic acid group, a phosphinic acid group, or the like in a mainchain or side chain, to the mixed solution for forming the coating film9.

Also, from the viewpoint of improving the strength, the thermalconductivity, the electrical conductivity, and the like of the coatingfilm 9, fillers and the like, for example, glass fibers, calciumcarbonate, aramid fibers, graphite, alumina, aluminum nitride, and boronnitride may be added to the mixed solution. Further, the circuit elementthat is an inner conductor located inside the element assembly is notlimited to the inductor. In addition, the configurations of someexamples may be combined.

INDUSTRIAL APPLICABILITY

As described above, the present disclosure is useful for the electroniccomponent and the method for manufacturing the same. In particular, inthe electronic component including an insulator containing a metalmagnetic powder, a resin coating film can be obtained on the insulatorand, thereby, an electronic component exhibiting excellent moistureresistance and chemical resistance can be obtained.

The invention claimed is:
 1. An electronic component comprising: a mainbody including an element assembly composed of a metal magnetic powderand an insulating resin and an inner conductor located inside theelement assembly; a coating film covering the main body; outerelectrodes connected to the inner conductor, wherein the coating filmcontains a reaction product of a resin and a cation of an elementconstituting the metal magnetic powder; and a magnetic path is disposedon an inner circumference of the inner conductor.
 2. The electroniccomponent according to claim 1, wherein the metal magnetic powder is apowder of Fe or an Fe alloy, and the inner conductor is Cu or Ag.